I know people who play a version with not even hunger added xD 1.8 Beta or something...All servers will be forced to go 1.9 but most of them will probably still attempt to stay as 1.8 as possible. Mojang included a feature to remove attack cooldown and plugins can easily fix the new armor values (maybe even command blocks) The only thing that may change is the cps registered by the game making a few 1.8/1.7 players mad but other than that everything will be nearly the same so sadly not all will be truly 1.9 :(